Hi Fred,
    I'm finding that many fab houses have settled into modified glass/epoxy systems for a lot of
the Hi Speed applications.  I would suggest running your design on a couple of different types.
Mitch suggested the G-Tek, which does well, but I would also consider Nelco's material (N-6000?-
Sorry all, if I got the wrong number).  Also check cleanliness levels.   JOHN WAITE

Mitch Morey wrote:

> Fred,
>
> I've personally done boards beyond 1Ghz with standard high Tg FR4
> material. The high Tg (>140) was for Z-axis stability. The board was
> exclusively 50 ohms impedance, and included a test coupon on the board
> itself. One thing we did was ask for impedance testing to be done to
> 200db levels instead of the standard 20db. This would show any and all
> discontinuities along the traces.
>
> My recommendation is to talk with your fab shop and determine what
> exactly they can do for you (technical input), and find out if they can
> fabricate using GETEK material (much like FR4, should be no additional
> costs) which has a lower and much more stable dielectric constant. My
> fab shops was dieing to give me GETEK boards, but this particular
> engineer wasn't familiar with it, and couldn't evaluate it properly.
>
> But then again, he did get boards at 1.2Ghz using standard FR4 material.
> Go figure?
>
> Good luck,
> Mitch Morey
> Sr PCB Designer
> NSI Communications
> San Diego CA 92121
> (619)657-5338
> [log in to unmask]
>
> >>> Fred Watt <[log in to unmask]> 05/21/98 07:25am >>>
>         Has anybody had any problems with FR-4 at 100 to 200 MHz?  I
> have several boards from several fabrication shops in which the signal
> loses amplitude above 80-100 MHz.  The boards are controlled
> impedance (50 Ohms) with 5 mil traces and 5 mil dielectrics.  The traces
> are about 6.5" long.
>         I would appreciate any comments on this subject.  The supplier of
> the material says that FR-4 should be good to 400 MHz.
>
> ################################################################
> TechNet E-Mail Forum provided as a free service by IPC using LISTSERV
> 1.8c
> ################################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in the body:
> To subscribe:   SUBSCRIBE TechNet <your full name>
> To unsubscribe:   SIGNOFF TechNet
> ################################################################
> Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional
> information.
> For technical support contact Hugo Scaramuzza at [log in to unmask] or
> 847-509-9700 ext.312
> ################################################################
>
> ################################################################
> TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
> ################################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
> To subscribe:   SUBSCRIBE TechNet <your full name>
> To unsubscribe:   SIGNOFF TechNet
> ################################################################
> Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
> For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
> ################################################################

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################